Agni Purana (Jyotisha Selections) · by Vyasa
Chapter 2 · War Astrology: Yogas, Nakshatras
युद्धजयार्णवः (योगाः नक्षत्राणि)
ईशः सप्तशिखा देवाः शब्दाद्याः पञ्च च स्वराः ।अ इ उ ए ओँ कलाश्च मूलं ब्रह्मेति कीर्तितम् ॥
In the full Agni Purana this is chapter 124, verse 6.
Ishana, the gods with seven flames, the five qualities beginning with sound, and the vowels a, i, u, e, o. The parts too. The root is called Brahma.
Simple meaning: Ishana, the seven-flamed gods, the five sense qualities and the five vowels are named. The root is Brahma.
काष्ठमध्ये यथा वह्निरप्रवृद्धो न दृश्यते ।
As fire is hidden in wood, Shiva and Shakti are hidden in the body.
आदौ शक्तिः समुत्पन्ना ओंकारस्वरभूषिता ।
First Shakti arose with Om. Then the dot stood in place with the vowel e.
जातो नाद उकारस्तु नदते हृदि संस्थितः ।
The sound u sits in the heart. The half-moon i shows the path to liberation.